Neuropsychological Functioning in Danish Gulf War Veterans

Research has shown that Danish Gulf War (GW) veterans reported a significantly higher prevalence of neuropsychological symptoms than did military controls 6 years after GW deployment. To explore the possible central nervous system determinants of these complaints, neuropsychological tests were administered to stratified, random samples of the Danish cohort of 916 GW-deployed veterans and 236 non–GW-deployed participants. Multivariate analyses of covariance were used to analyze neuropsychological test outcomes among the 215 male participants (143 GW-deployed and 72 non–GW-deployed soldiers). No significant differences in neuropsychological test performances were found between the GW-deployed and non–GW-deployed groups. Troops deployed to the GW reported significantly more mood complaints (i.e., fatigue and confusion) than their nondeployed counterparts. Because they were assigned to the Gulf region during the postcombat phase, Danish GW soldiers differed from the majority of American GW-deployed troops in military assignments and possible toxicant exposures.     

Cognitive Functioning in Treatment-Seeking Gulf War Veterans: Pyridostigmine Bromide Use and PTSD

Gulf War (GW) deployed veterans have reported health symptoms since returning from the war that suggest dysfunction of the central nervous system (CNS). These symptoms include memory and concentration difficulties, fatigue, and headaches. Leading hypotheses for the etiology of these cognitive complaints include psychological factors and/or exposures to chemicals with neurotoxic properties. In this study, cognitive functioning was compared in treatment-seeking GW-deployed veterans and a treatment-seeking non–GW-deployed veteran control group. Results indicated that GW-deployed veterans performed significantly worse than the comparison group on tests of attention, visuospatial skills, visual memory, and mood. GW-deployed veterans who reported taking pyridostigmine bromide (PB) performed worse than GW-deployed veterans without PB use on executive system tasks. Treatment-seeking GW-deployed veterans with diagnoses of posttraumatic stress disorder (PTSD) did not differ on cognitive test measures compared with GW-deployed veterans without PTSD. No interaction effect of PTSD and PB use was found.     

Scheduling Processes in Working Memory: Instructions Control the Order of Memory Search and Mental Arithmetic

Humans must often use working memory to execute processes one at a time because of its limited capacity. Two experiments tested where limits in access to working memory occur. Subjects searched a short-term memory set for one stimulus digit and performed mental arithmetic with another stimulus digit. In one experiment, they were told to carry out the mental arithmetic before the memory search and to make the arithmetic response first. In the other, they were instructed to perform the tasks in the opposite order. The overt responses were executed in the prescribed order. Moreover, the covert working memory processes were executed in the prescribed order, as revealed by a critical path network analysis of reaction times. Results are explained in terms of a double-bottleneck model in which central processes and responses are constrained to be carried out for one task at a time.     

Lateralized warning tones produce typical irrelevant-location effects on choice reactions

Simon, Acosta, and Mewaldt (1975) reported an experiment in which a 200-Hz warning-tone, presented in the left or right ear, was followed by an imperative stimulus of 500 Hz in either ear, to which a left- or right-key press was to be made. Simon et al. found a correspondence effect for warning location and response location (i.e., faster reactions when warning and response locations corresponded than when they did not) when the stimulus-response mapping was incompatible but not when it was compatible. These findings stand in contrast to typical results of (1) a correspondence effect for irrelevant location information when the mapping is compatible and (2) a reversed correspondence effect (i.e., faster responses when stimulus and response location do not correspond) when the mapping is incompatible. We conducted a direct replication of Simon et al.’s experiment and another experiment that differed only in the imperative stimulus being visual, in order to determine whether there are unique aspects of their method that yield atypical results. Our results failed to replicate those reported by Simon et al. but instead showed the patterns of correspondence effects typically found with other procedures, suggesting that the warning-signal method produces irrelevant-location effects consistent with those produced by other methods.     

Frequency and duration of hierarchy item exposure in a systematic desensitization analogue

Little is known regarding the importance of stimulus presentation variables in desensitization. A repeated measures factorial research design was utilized to investigate the role of hierarchy item frequency and duration in a desensitization analogue. Two frequency levels (1 and 3) and three total duration levels (3,12 and 30 sec) were combined to form six treatment groups; an additional no-treatment control group was also used. Results in both overt behavioral and subjective fear response modes suggest that single exposures are preferable, but that this preference is localized primarily in the longer total duration range. Long single exposures to hierarchy items yielded the greatest and most persistent changes in both response modes. It is suggested that clinicians utilize item presentations of this sort to determine their efficacy in actual therapy conditions. Choice of technique for assessing change and the utility of analogue studies are also briefly discussed.     

An analysis of U-shaped metacontrast

Using a brightness-discrimination task similar to that employed by Bernstein, Proctor, Proctor, and Schurman (1973), masking functions were obtained in two experiments. In Experiment I, test stimulus (TS) and mask stimulus (MS) energies were held constant but luminance and duration were varied reciprocally. The obtained masking functions, plotted as a function of stimulus onset asynchrony (SOA), were of an essentially identical U shape. This suggests that (a) SOA is a more suitable measure of delay than interstimulus interval, and (b) Bloch’s law holds for the requisite discrimination. In Experiment II, TS luminance and MS luminance were varied independently. This was to see whether the MS served as a frame of reference at short SOA, as suggested previously (Bernstein et al, 1973). The results were that this was, in fact, the case and that the transition from comparative to absolute judgment strategies as SOA increases is a major contributor to U-shaped masking functions.